(423e) Origins of High-Pressure Structural Stability, Elasticity and Self-Healing Property in Ligand Capped Nanoparticles Supercrystals

Ligand capped nanoparticles spontaneously assemble into supercrystals that have remarkable tunable properties. In these solids, the ligands, which link the metallic and semiconducting nanoparticles, play the central role in determining structural symmetry and their properties. These linker molecules can combine specific optical, electronic, or magnetic functionality of nanoparticles with the flexibility of self-assembly, and provide promising pathways for the development of tunable materials. However, the current development of these ligand decorated supercrystals is limited by many factors. First, a generic strategy to control the morphology, long-range order, lattice spacing and tailoring their properties is not yet established. Second, these materials exhibit a wide variation in its response to external conditions, particular pressure and deformation. The underlying microscopic origins of their unusual variation in mechanical properties remains unresolved. Furthermore, how and when failure of supercrystals under stress occur is an open question in materials science. Here, we employ large-scale molecular dynamic (MD) simulations to address these issues. We systematically investigate the role of ligands on the crystalline symmetry, pressure behavior, elasticity, deformation and self-healing properties of a model supercrystal, made of oleic acid capped PbS nanoparticles. The interplay between deflection and interdigitation of ligands are shown to be critical for crystalline symmetry and maintaining high-pressure structural stability. The elasticity viz., the Young’s modulus and bulk modulus are shown to be strongly correlated with the ligand concentration. Further, our MD simulations reveal molecular mechanisms of elastic deformation and healing in a supercrystal. We show inter-relationships between elastic deformation, self-healing ability and strain rate. These interconnections provide guidance towards the design of supercrystals with improved stability, and tunable mechanical property for future nanotechnology applications.